The cloudfront URL’s are the result of asset optimization, as configured on your site’s deploy settings page most of the way down:

Things that get optimized (which don’t include the <link> tag at present) will get rewritten to cloudfront URL’s. HOWEVER all content we serve is served from a CDN - that’s just the CDN we use for optimized assets. All traffic from netlify comes from some part of some CDN

If you want things to be consistent, turn off that feature in our UI. But hopefully things work normally, even if they look a little weird in the source code?